The oxygen atoms in Earth's atmosphere were created?

Question

The oxygen atoms in Earth's atmosphere were created...

when atoms first formed, about half a million years after the beginning of the Universe.

during the Big Bang.

during the formation of the Earth.

by nuclear fusion in massive stars.

Answer 1

i believe inside stars,but i know you think why didn't it burn up ,well technically it did .it was bound up as compounds of other elements,then in the cooler climate of space then the earth ,forces could unlock the oxygen and release it as a gas................im no chemist but i think it's similar to that........................tom

Answer 2

by nuclear fusion in massive stars

Answer 3

during the formation of the Earth